In general, a dishwasher is an appliance that washes dishes, cookware, etc. (hereinafter referred to as an “object to be washed”) by removing foreign substances such as food waste from an object to be washed using a detergent and wash water.
Typically, a dishwasher includes a tub defining a washing compartment, a dish rack provided in the tub, in which an object to be washed is accommodated, a spray arm for spraying wash water to the dish rack, a sump for retaining wash water, and a supply passage, through which the wash water retained in the sump is supplied to the spray arm.
Recently, a dishwasher capable of spraying wash water evenly toward an object to be washed through rotation of the spray arm has been developed. Further, in order to improve washing performance, the spray arm is structured such that a portion thereof performs a reciprocating movement (rolling) along a predetermined circular arc path using the rotating force of the spray arm.